Get help with sizing common rod building components.
The first measurement in a Tip-Top is the Inside Diameter (I.D.) of the ring (eyelet) in Millimeters. Generally, the I.D. of the ring will match the smallest guide on the rod. Standard sizes are 6, 8 and 10mm for conventional rods, while heavier salt
All guides sizes are measured by the outside diameter of the ceramic insert ring, or in other words, the inside diameter of the metal frame – without the ceramic ring in it. For example, a guide with an insert ring OD measuring ~20mm is a size 20.